(Meth)acrylic acid is generally prepared by gas phase oxidation of propane, propylene, (meth)acrolein, and the like in the presence of a catalyst. For example, propane, propylene, and the like are converted to (meth)acrylic acid through (meth)acrolein by gas phase oxidation in the presence of an appropriate catalyst in a reactor, and a reaction product mixed gas including (meth)acrylic acid, non-reacted propane or propylene, (meth)acrolein, inert gas, carbon dioxide, water vapor, and various organic by-products (acetic acid, high boiling point by-products, and the like) is obtained in the back end of the reactor.
The (meth)acrylic acid-containing mixed gas contacts an absorption solvent such as process water and the like in a (meth)acrylic acid absorption tower, and is recovered as a (meth)acrylic acid aqueous solution. Further, (meth)acrylic acid-stripped insoluble gas is recycled for a synthesis reaction of (meth)acrylic acid, and a part thereof is incinerated, converted into harmless gas, and discharged. The (meth)acrylic acid aqueous solution is distilled and purified while passing through a water separation tower and the like, to obtain (meth)acrylic acid.
Meanwhile, in order to improve the recovery efficiency of (meth)acrylic acid, various methods of controlling process conditions or process sequence and the like have been suggested. Among them, as a method for separating water and acetic acid from the (meth)acrylic acid aqueous solution obtained in the (meth)acrylic acid absorption tower, an azeotropic distillation method is known, wherein acetic acid, the main by-product of a (meth)acrylic acid process, is recovered from the upper part of the water separation tower together with water using a hydrophobic azeotropic solvent in the water separation tower, and (meth)acrylic acid is recovered from the lower part of the water separation tower.
Particularly, the inventors suggested a method of recycling acetic acid-containing waste water that is recovered from the upper part of the water separation tower to the (meth)acrylic acid absorption tower and reusing it, in Korean Laid-Open Patent No. 2009-0041355.
The method of distilling a (meth)acrylic acid aqueous solution using a hydrophobic azeotropic solvent in the water separation tower may reduce the amount of waste water and simultaneously effectively prevent introduction of organic substances, and simplify a subsequent purification step.
However, the above method and previously disclosed recovery methods of (meth)acrylic acid have problems in that a very large amount of energy is consumed in the process of distilling a (meth)acrylic acid aqueous solution, and normal operation cannot be conducted due to the production of polymers by polymerization of (meth)acrylic acid, and thus operation stability is lowered.